If there is one ingredient that generates polarizing opinions, it is the chili pepper: Some people cannot get enough of them, while others try to avoid it at all cost. But chilies are to be found everywhere in modern and traditional cuisines. Universally recognized for packing a spicy punch, chili infused dishes are denoted with red stars on some menus.

Chilies are defined as any pepper that include the chemical compound capsaicin. Capsaicin, unlike other compounds found in food, is a chemesthetic (a chemical that activates receptors associated with pain and touch) so it produces a burning sensation, rather than a taste or smell. In short, the more the capsaicin, the more the spice.

Here is everything you need to know about chilies:

Buying and storing: Fresh chilies, particularly popular variations like jalapeños can be found in the produce aisle of nearly any grocery store. Before purchasing, make sure that they are firm to the touch, and that the skin is unblemished and smooth, rather than wrinkled. Wrinkled chilies are past their prime, and will not yield a lot of flavor. Chilies can be stored for up to two weeks in a dry paper towel inside of a plastic bag, placed either in your refrigerator or in a cool, dark place, like an enclosed pantry.

Cooking with chilies: You probably know by now that it is a bad idea to touch your eye after handling a chili, but some chilies contain so much spice that it is necessary to handle them with gloves, as the oils can burn bare skin. If you do not have any gloves at the ready, coat your hands in oil before handling particularly hot peppers - the oil from the peppers will stick to the oil, rather than to your skin. If you accidentally touch hot pepper, soak your hands in milk or yogurt until the burning sensation subsides - the idea being that chili oil is more soluble in fats and oils than it is in water.

For those who are not huge fans of spice, there are several ways to cut down on the heat. The majority of the spice, or capsaicin, is contained in the spongy white mass directly under the stem that holds the seeds. To reduce the spice, remove this part of the chili, along with the seeds, using a spoon or paring knife. For recipes that require an entire chili, try to remove the seeds by first removing the stem and going in through the top to maintain the structure of the chili. Once done, submerge the chili in cold water for several minutes to further remove heat, then drain and pat dry.

Varieties of chilies: There are countless variations of peppers, but there are only about ten that you need to know about because of their popularity. Three of the greatest variations between peppers are their color, origin, and spice level, measured in Scoville units. For reference, Tabasco contains five thousand to ten thousand Scoville heat units (SHUs), while ghost peppers can have as many as one million SHUs. A good rule of thumb is: The smaller the pepper variety, the spicier the chili. The majority of the peppers mentioned here will fall somewhere between one thousand to a hundred thousand Scoville units.

Cayenne peppers are often used in dishes like chili and salsa. In its purest form, it can be rated as high as fifty thousand SHUs, but is far less spicy in its powdered form, which is commonly used. It is also a key ingredient in many hot sauces.

Jalapeños are the most readily available peppers and are used for mild dishes like green salsa. When smoked and dried, they are called chipotles.

Thai chilies, also known as the bird's eye chili in its dried form, is commonly found in Southeast Asia, and measures around hundred thousand SHUs. It is used extensively in Thai and Vietnamese cuisines, in curries, stir-fries, and Thai salads.

Serranos are similar to jalapeños but are crisper and spicier - they are often used in Mexican cuisine in dishes such as pico de gallo and guacamole.

Poblano, also known as ancho chilies when dried, are much larger than other pepper variations and are very mild. They are found in dishes like chilies rellenos.

Habaneros are extremely spicy, so only use them if you have an appetite for heat. They can be delicious in salsas.

And then there are the incredibly spicy chilies for thrill-seekers, like the ghost pepper, or bhut jolokia, and the Carolina Reaper. Both have enjoyed the title as the spiciest pepper in the world, and are used, highly diluted, in some hot sauces and dishes by the truly brave.

Using whole chilies versus dried or powdered: As with other produce, fresh chilies contain the most flavor, but some recipes call for dried or powdered variations. The best dried chilies are those that have been sun-dried and are slightly flexible, rather than completely dried out. The benefit of dried chilies is that they can be stored in a cool, dark place for up to a year or can be ground into powder. Many recipes call for chili powder which is a primary ingredient in chili con carne. This powder is not pure chili, but rather a combination of dried chili pods and other spices like cumin, oregano, and garlic powder. Still, chili and chili powder can be used interchangeably for most recipes. Similarly, chili flakes are made out of a variety of dried and crushed red chilies, including ancho, bell, and cayenne.